Cobalt oxide spinel, identified by the empirical formula Co.sub.3 O.sub.4, is known. Spinels are a class of compounds with a particular crystal structure denoted by the general formula AB.sub.2 O.sub.4, where A and B can be the same or different metals as long as the total metal valence equals eight. It is also known that electroconductive substrates having a coating of Co.sub.3 O.sub.4 are useful as an electrode material, especially anode material, for use in electrolytic processes, such as brine electrolysis, chlorine cells, chlorate cells, and the like.
It is also known that various metal cations can be substituted into the cobalt oxide spinels to produce bimetal spinels, trimetal spinels, and polymetal spinels, where cobalt comprises only one of the metals in the crystalline oxide lattice structure.
We have now found, surprisingly and unexpectedly, that fluoride anions can be substituted into the cobalt oxide spinels, replacing a portion of the oxygen anions.